// Ceres Solver - A fast non-linear least squares minimizer
// Copyright 2023 Google Inc. All rights reserved.
// http://ceres-solver.org/
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// Author: sameeragarwal@google.com (Sameer Agarwal)

#include "ceres/block_structure.h"

#include <vector>

#include "absl/log/check.h"

namespace ceres::internal {

bool CellLessThan(const Cell& lhs, const Cell& rhs) {
  if (lhs.block_id == rhs.block_id) {
    return (lhs.position < rhs.position);
  }
  return (lhs.block_id < rhs.block_id);
}

std::vector<Block> Tail(const std::vector<Block>& blocks, int n) {
  CHECK_LE(n, blocks.size());
  std::vector<Block> tail;
  const int num_blocks = blocks.size();
  const int start = num_blocks - n;

  int position = 0;
  tail.reserve(n);
  for (int i = start; i < num_blocks; ++i) {
    tail.emplace_back(blocks[i].size, position);
    position += blocks[i].size;
  }

  return tail;
}

int SumSquaredSizes(const std::vector<Block>& blocks) {
  int sum = 0;
  for (const auto& b : blocks) {
    sum += b.size * b.size;
  }
  return sum;
}

}  // namespace ceres::internal
